1. Field of the Invention
The present invention relates to methods and apparatus for assembling vent valves; and more particularly, to such a method and apparatus for assembling thin film vent valves.
2. Description of the Prior Art
One utilization for vent valves are in packages commonly referred to as "squeeze pump" packages. Such packages typically have a resilient outer bottle and a flexible inner bag. As the resilient outer bottle is squeezed, a positive pressure develops in the space between the flexible bag and the squeeze bottle. This increased air pressure around the flexible bag causes the bag to collapse against the product. Fluid product is then typically forced to flow through a fluid product valve and out of the squeeze pump package through a discharge orifice. Upon releasing the squeeze force, a vent valve is often utilized to permit atmospheric air to be drawn into the space between the flexible bag and the squeeze bottle as the outer bottle returns towards its original shape.
Common vent valves include ball check valves, rubber duckbill valves, rubber umbrella valves, and thin film valves. Due to material cost savings, thin film valves are potentially very economical when compared with other types of reliable vent valves. Thin film valves have previously included a thin film of plastic material attached adjacent to one or more apertures such that the thin film material closes (thereby sealing) the apertures in response to a positive (i.e., superatmospheric) pressure in the bottle, and unseals the apertures in response to a negative (i.e., subatmospheric) pressure therein. An advantage of such thin film valves is that a very low cracking pressure will initiate venting. To date, however, the thin film material of such vent valves have typically been attached (via heat sealing or adhesive) to a flat, inner surface, of a bottle. Since installation of the thin film material is normally against an inner surface of the bottle, placement and attachment may be difficult operations and/or may require that the package be made of several components to allow ready access to the film attachment point.
The present invention provides a method and apparatus for assembling a thin film beam spring vent valve which does not require attachment of the thin film material to an inner surface lo of the bottle (although such attachment may be utilized), the resilience of the thin film material helps maintain the thin film material in the proper location adjacent the aperture.